Quantitative characterization of the microstructure of 16MND5 steel in vessel

Ce travail de thèse concerne l’acier 16MND5 des cuves des Réacteurs à Eau Préssurisée (REP).L’étude vise à caractériser de manière quantitative la microstructure et à comprendre l’effet desparamètres influents (vitesse de refroidissement, température de revenu …) sur sa formation. D’unpoint de vue expérimental, l’étude est menée grâce à l’utilisation des techniques d’observationcomme la métallographie, le MET, MEB et l’EBSD, et la réalisation de traitements thermiquescontrôlés (dilatométrie notamment).Ces observations visent à identifier les différents constituants de l’acier et de déterminer lesgrandeurs quantitatives les caractériser (tailles, fractions volumiques des différentes phases ainsique leurs orientations cristallographiques).Nous avons dans un premier temps caractérisé de manière complète et quantitative, lamicrostructure de l’acier 16MND5 à l’état de réception (trempé et revenu). L’étude a permis demontrer qu’il existe un gradient de microstructure entre la peau interne et le coeur de l’épaisseur dela virole. La microstructure à coeur est constituée de ferrite proeutectoïde, de bainite et d’amas decarbures, tandis qu’en peau interne on est en présence de bainite et d’amas de carbures.Une campagne d’essais de dilatométrie a été réalisée afin de simuler la microstructure brute detrempe de l’acier 16MND5 et d’observer l’effet de la vitesse de refroidissement, des températuresde transformation sur la microstructure des aciers de cuve. Ces essais ont révélé que lamicrostructure de l’acier 16MND5 après refroidissement est constituée de bainite, d’îlots demartensite et d’austénite résiduelle (M-A) enrichie en carbone. Ce sont ces îlots M-A qui donnentnaissance aux amas de carbures lors du revenu final.L’effet de la composition chimique de cet acier a été étudié grâce à l’utilisation d’une tôle ayant unecomposition chimique plus riche en carbone et en éléments d’alliages. Ce travail a montré quel’augmentation des teneurs en carbone et en éléments d’alliages modifiaient la morphologie et lacristallographie de la ferrite.L’étude des comportements mécaniques des constituants présents en peau interne, quart épaisseur etmi épaisseur a été réalisée grâce à des essais de résilience sur des éprouvettes de mini charpy. Cetteétude a permis de montrer qu’à basse température (-120°C) la peau interne présente de meilleurespropriétés de résilience que le quart et la mi épaisseur de la virole. Des examens de la surfacelatérale des éprouvettes de Charpy ont montré que la présence de ferrite proeutectoïde favorise lagermination de micro-fissures de clivage.Reactor pressure vessel is the second security barrier of the nuclear reactor and it is elaboratedwith a low carbon steel ( C-0.16%). Due to the large size of the ferrule there is temperatureand cooling rate gradient, which lead to microstructure gradient. To develop predictive modelit is necessary to well describe the microstructure which depend to the processing parameters.We focuse our work in investigating the effect of the processing parameters (cooling rate,chemical composition...) on the final microstructure during phase transformation.To get these informations and better describe the microstructure, we have used someexperimental technics like SEM, EBSD, TEM and Optical Microscopy. The steel used is alow carbon steel with a composition of C-0.16%, Mn-1.32%, Ni-0.72%, Mo-0.49%, Si-0.23%, Cr-0.23%, P-0.010%, S-0.004%. The material has been tempered in the range 635°C-660°C after cooling. Three positions have been chosen for examinations, because the coolingrate is not the same between the center and the edge of the material. The results of theobservations made in the different scale, indicate that the microstructure is mainly baniticwith bainitic ferrite and cementite precipitates. Examinations of the precipitates withextractive replicas in TEM reveal that morphology of cementite particles is complex they arecylinder-shaped particles, short bars particles and skeletal particles. OrientationsRelationships (OR) have been determined between ferrite and cementite particles with thinfoils in TEM by using Selected Area Diffraction, in a large number areas the Isaichev andBagaryatskii OR have been observed, a little Pitsch Petch OR have been obtained. The EBSDmap shows that the bainitic ferrite morphologies are both lath like and polygon. Themisorientations inside the laths are very small (0.5° misorientation point to point) andbetween laths we have the range 49-60° misorientation. The profile of misorientationsbetween point to point indicates higher frequency for the range 49-60°. Charpy test have beenperformed to analyze the effect of the microstructure on the fracture energy at lowtemperature. The results show that the fracture energy decreases when the content ofproeutectoid ferrite is high

Effect of planting date on growth, development, and yield of grain sorghum hybrids

Master of ScienceDepartment of AgronomyScott A. StaggenborgIn Kansas, productivity of grain sorghum [Sorghum bicolor (L.) Moench] is affected by weather conditions at planting and during pollination. Planting date management and selection of hybrid maturity group can help to avoid severe environmental stresses during these sensitive stages. The hypothesis of the study was that late May planting improves grain sorghum yield, growth and development compared with late June planting. The objectives of this research were to investigate the influence of planting dates on growth, development, and yield of different grain sorghum hybrids, and to determine the optimal planting date and hybrid combination for maximum biomass and grains production. Three sorghum hybrids (early, medium , and late maturing) were planted in late May and late June without irrigation in Kansas at Manhattan/Ashland Bottom Research Station, and Hutchinson in 2010; and at Manhattan/North Farm and Hutchinson in 2011. Data on leaf area index, dry matter production, harvest index, yield and yield components were collected. Grain yield and yield components were influenced by planting date depending on environmental conditions. At Manhattan (2010), greater grain yield, number of heads per plant, harvest index, and leaf-area were obtained with late-June planting compared with late May planting, while at Hutchinson (2010) greater yield was obtained with late May planting for all hybrids. The yield component most affected at Hutchinson was the number of kernels panicle-1 and plant density. Late-May planting was favorable for late maturing hybrid (P84G62) in all locations. However, the yield of early maturing hybrid (DKS 28-05) and medium maturing hybrid (DKS 37-07) was less affected by delayed planting. The effects of planting dates on growth, development, and yield of grain sorghum hybrids were found to be variable among hybrid maturity groups and locations

Caractérisation quantitative de la microstructure de l'acier 16MND5 des cuves de réacteurs nucléaires à eau pressurisée

Ce travail de thèse concerne l acier 16MND5 des cuves des Réacteurs à Eau Préssurisée (REP).L étude vise à caractériser de manière quantitative la microstructure et à comprendre l effet desparamètres influents (vitesse de refroidissement, température de revenu ) sur sa formation. D unpoint de vue expérimental, l étude est menée grâce à l utilisation des techniques d observationcomme la métallographie, le MET, MEB et l EBSD, et la réalisation de traitements thermiquescontrôlés (dilatométrie notamment).Ces observations visent à identifier les différents constituants de l acier et de déterminer lesgrandeurs quantitatives les caractériser (tailles, fractions volumiques des différentes phases ainsique leurs orientations cristallographiques).Nous avons dans un premier temps caractérisé de manière complète et quantitative, lamicrostructure de l acier 16MND5 à l état de réception (trempé et revenu). L étude a permis demontrer qu il existe un gradient de microstructure entre la peau interne et le coeur de l épaisseur dela virole. La microstructure à coeur est constituée de ferrite proeutectoïde, de bainite et d amas decarbures, tandis qu en peau interne on est en présence de bainite et d amas de carbures.Une campagne d essais de dilatométrie a été réalisée afin de simuler la microstructure brute detrempe de l acier 16MND5 et d observer l effet de la vitesse de refroidissement, des températuresde transformation sur la microstructure des aciers de cuve. Ces essais ont révélé que lamicrostructure de l acier 16MND5 après refroidissement est constituée de bainite, d îlots demartensite et d austénite résiduelle (M-A) enrichie en carbone. Ce sont ces îlots M-A qui donnentnaissance aux amas de carbures lors du revenu final.L effet de la composition chimique de cet acier a été étudié grâce à l utilisation d une tôle ayant unecomposition chimique plus riche en carbone et en éléments d alliages. Ce travail a montré quel augmentation des teneurs en carbone et en éléments d alliages modifiaient la morphologie et lacristallographie de la ferrite.L étude des comportements mécaniques des constituants présents en peau interne, quart épaisseur etmi épaisseur a été réalisée grâce à des essais de résilience sur des éprouvettes de mini charpy. Cetteétude a permis de montrer qu à basse température (-120C) la peau interne présente de meilleurespropriétés de résilience que le quart et la mi épaisseur de la virole. Des examens de la surfacelatérale des éprouvettes de Charpy ont montré que la présence de ferrite proeutectoïde favorise lagermination de micro-fissures de clivage.Reactor pressure vessel is the second security barrier of the nuclear reactor and it is elaboratedwith a low carbon steel ( C-0.16%). Due to the large size of the ferrule there is temperatureand cooling rate gradient, which lead to microstructure gradient. To develop predictive modelit is necessary to well describe the microstructure which depend to the processing parameters.We focuse our work in investigating the effect of the processing parameters (cooling rate,chemical composition...) on the final microstructure during phase transformation.To get these informations and better describe the microstructure, we have used someexperimental technics like SEM, EBSD, TEM and Optical Microscopy. The steel used is alow carbon steel with a composition of C-0.16%, Mn-1.32%, Ni-0.72%, Mo-0.49%, Si-0.23%, Cr-0.23%, P-0.010%, S-0.004%. The material has been tempered in the range 635C-660C after cooling. Three positions have been chosen for examinations, because the coolingrate is not the same between the center and the edge of the material. The results of theobservations made in the different scale, indicate that the microstructure is mainly baniticwith bainitic ferrite and cementite precipitates. Examinations of the precipitates withextractive replicas in TEM reveal that morphology of cementite particles is complex they arecylinder-shaped particles, short bars particles and skeletal particles. OrientationsRelationships (OR) have been determined between ferrite and cementite particles with thinfoils in TEM by using Selected Area Diffraction, in a large number areas the Isaichev andBagaryatskii OR have been observed, a little Pitsch Petch OR have been obtained. The EBSDmap shows that the bainitic ferrite morphologies are both lath like and polygon. Themisorientations inside the laths are very small (0.5 misorientation point to point) andbetween laths we have the range 49-60 misorientation. The profile of misorientationsbetween point to point indicates higher frequency for the range 49-60. Charpy test have beenperformed to analyze the effect of the microstructure on the fracture energy at lowtemperature. The results show that the fracture energy decreases when the content ofproeutectoid ferrite is high.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Investigations of the microstructural response to a cold forging process of the 6082-T6 alloy

International audienceThe microstructure of 6082 aluminium alloy in artificial aged condition was investigated before and after cold forming. The cold forming process was performed at room temperature with and without lubricant. An in depth microstructure investigation has been carried out through electron backscatter diffraction (EBSD) analysis. Different approaches were considered to quantify the plastic strain: the Line Segment Method (LSM) and the study of misorientations trough the Kernel Average Misorientation (KAM), the Grain Orientation Spread (GOS) and the Grain Average Misorientation (GAM). The evidence of intermetallic particles removal from their location during plastic deformation was observed. Values of plastic strain lower than 0.1 did not affect the grain size itself. Nonetheless it induced the development of sub-structures which may lead to the hardening of the alloy

Perception by farmers of the determinants of irrigated rice yield in Mali

International audienceAbstractRecommendations for crop management are based on agronomic diagnoses of yield determinants at plot scale usually without the farmers being involved in the evaluation process. Farmers may consequently not apply the recommendations that do not account for their own perception of yield determination. We assumed that (i) farmers have their own perceptions of yield determination; (ii) it is possible to access these perceptions through individual discussions with farmers; (iii) subsequent group discussions allow knowledge to be exchanged between farmers and a common viewpoint to be reached; (iv) agronomists can use this common viewpoint as a basis for building improved solutions in collaboration with the farmers. In this study, we used participatory methods to identify and discuss the visual references the farmers consider the crop growth as indicators to forecast the yield of their plot and the drivers they think affect these indicators. The study was conducted in two sites in the Office du Niger irrigated rice scheme in Mali and comprised three steps: (i) individual discussions with rice producers about their perception of how yield is determined, (ii) group discussions to share their individual perceptions and reach a common viewpoint, (iii) analysis of these perceptions. Seven production indicators and 29 factors that may affect these indicators were identified. The three mains indicators used by farmers were tiller abundance, hill density, and grain weight per panicle. Crop practices and constraints may prevent farmers from achieving high yields, such as a delay in the supply of fertilizers or in crop establishment. They had a complex perception of yield determination that was often close to agronomic knowledge. Here we demonstrate for the first time that farmers in the Office du Niger scheme have technical knowledge to which extension services could refer to provide relevant advice and tools for managing their constraints and improving yield

The international experience of in-situ recovery of the DCD heart: a multicentre retrospective observational study.

BackgroundHeart transplantation is an effective treatment offering the best recovery in both quality and quantity of life in those affected by refractory, severe heart failure. However, transplantation is limited by donor organ availability. The reintroduction of heart donation after the circulatory determination of death (DCD) in 2014 offered an uplift in transplant activity by 30%. Thoraco-abdominal normothermic regional perfusion (taNRP) enables in-situ reperfusion of the DCD heart. The objective of this paper is to assess the clinical outcomes of DCD donor hearts recovered and transplanted from donors undergoing taNRP.MethodThis was a multicentre retrospective observational study. Outcomes included functional warm ischaemic time, use of mechanical support immediately following transplantation, perioperative and long-term actuarial survival and incidence of acute rejection requiring treatment. 157 taNRP DCD heart transplants, performed between February 2, 2015, and July 29, 2022, have been included from 15 major transplant centres worldwide including the UK, Spain, the USA and Belgium. 673 donations after the neurological determination of death (DBD) heart transplantations from the same centres were used as a comparison group for survival.FindingstaNRP resulted in a 23% increase in heart transplantation activity. Survival was similar in the taNRP group when compared to DBD. 30-day survival was 96.8% ([92.5%-98.6%] 95% CI, n = 156), 1-year survival was 93.2% ([87.7%-96.3%] 95% CI, n = 72) and 5-year survival was 84.3% ([69.6%-92.2%] 95% CI, n = 13).InterpretationOur study suggests that taNRP provides a significant boost to heart transplantation activity. The survival rates of taNRP are comparable to those obtained for DBD transplantation in this study. The similar survival may in part be related to a short warm ischaemic time or through a possible selection bias of younger donors, this being an uncontrolled observational study. Therefore, our study suggests that taNRP offers an effective method of organ preservation and procurement. This early success of the technique warrants further investigation and use.FundingNone of the authors have a financial relationship with a commercial entity that has an interest in the subject

The international experience of in-situ recovery of the DCD heart: a multicentre retrospective observational study.

BACKGROUND: Heart transplantation is an effective treatment offering the best recovery in both quality and quantity of life in those affected by refractory, severe heart failure. However, transplantation is limited by donor organ availability. The reintroduction of heart donation after the circulatory determination of death (DCD) in 2014 offered an uplift in transplant activity by 30%. Thoraco-abdominal normothermic regional perfusion (taNRP) enables in-situ reperfusion of the DCD heart. The objective of this paper is to assess the clinical outcomes of DCD donor hearts recovered and transplanted from donors undergoing taNRP. METHOD: This was a multicentre retrospective observational study. Outcomes included functional warm ischaemic time, use of mechanical support immediately following transplantation, perioperative and long-term actuarial survival and incidence of acute rejection requiring treatment. 157 taNRP DCD heart transplants, performed between February 2, 2015, and July 29, 2022, have been included from 15 major transplant centres worldwide including the UK, Spain, the USA and Belgium. 673 donations after the neurological determination of death (DBD) heart transplantations from the same centres were used as a comparison group for survival. FINDINGS: taNRP resulted in a 23% increase in heart transplantation activity. Survival was similar in the taNRP group when compared to DBD. 30-day survival was 96.8% ([92.5%-98.6%] 95% CI, n = 156), 1-year survival was 93.2% ([87.7%-96.3%] 95% CI, n = 72) and 5-year survival was 84.3% ([69.6%-92.2%] 95% CI, n = 13). INTERPRETATION: Our study suggests that taNRP provides a significant boost to heart transplantation activity. The survival rates of taNRP are comparable to those obtained for DBD transplantation in this study. The similar survival may in part be related to a short warm ischaemic time or through a possible selection bias of younger donors, this being an uncontrolled observational study. Therefore, our study suggests that taNRP offers an effective method of organ preservation and procurement. This early success of the technique warrants further investigation and use. FUNDING: None of the authors have a financial relationship with a commercial entity that has an interest in the subject

The international experience of in-situ recovery of the DCD heart: a multicentre retrospective observational study.

peer reviewed[en] BACKGROUND: Heart transplantation is an effective treatment offering the best recovery in both quality and quantity of life in those affected by refractory, severe heart failure. However, transplantation is limited by donor organ availability. The reintroduction of heart donation after the circulatory determination of death (DCD) in 2014 offered an uplift in transplant activity by 30%. Thoraco-abdominal normothermic regional perfusion (taNRP) enables in-situ reperfusion of the DCD heart. The objective of this paper is to assess the clinical outcomes of DCD donor hearts recovered and transplanted from donors undergoing taNRP. METHOD: This was a multicentre retrospective observational study. Outcomes included functional warm ischaemic time, use of mechanical support immediately following transplantation, perioperative and long-term actuarial survival and incidence of acute rejection requiring treatment. 157 taNRP DCD heart transplants, performed between February 2, 2015, and July 29, 2022, have been included from 15 major transplant centres worldwide including the UK, Spain, the USA and Belgium. 673 donations after the neurological determination of death (DBD) heart transplantations from the same centres were used as a comparison group for survival. FINDINGS: taNRP resulted in a 23% increase in heart transplantation activity. Survival was similar in the taNRP group when compared to DBD. 30-day survival was 96.8% ([92.5%-98.6%] 95% CI, n = 156), 1-year survival was 93.2% ([87.7%-96.3%] 95% CI, n = 72) and 5-year survival was 84.3% ([69.6%-92.2%] 95% CI, n = 13). INTERPRETATION: Our study suggests that taNRP provides a significant boost to heart transplantation activity. The survival rates of taNRP are comparable to those obtained for DBD transplantation in this study. The similar survival may in part be related to a short warm ischaemic time or through a possible selection bias of younger donors, this being an uncontrolled observational study. Therefore, our study suggests that taNRP offers an effective method of organ preservation and procurement. This early success of the technique warrants further investigation and use. FUNDING: None of the authors have a financial relationship with a commercial entity that has an interest in the subject